add flak8 check

.flake8

@@ -0,0 +1,2 @@
+[flake8]
+max-line-length = 120

.pre-commit-config.yaml

@@ -28,3 +28,7 @@ repos:
     hooks:
       - id: isort
         args: [--profile, black, --multi-line, "3"]
+  - repo: https://github.com/PyCQA/flake8
+    rev: 4.0.1
+    hooks:
+      - id: flake8